Finding the Fourth Proportional to 2,105.60, 2,905.72 and 1,221.68

Step by Step Solution

1. Step 1: Write the proportion equation
   2,105.60 : 2,905.72 = 1,221.68 : x
2. Step 2: Convert to fraction form
   2,105.60/2,905.72 = 1,221.68/x
3. Step 3: Cross multiply
   2,105.60x = 2,905.72 × 1,221.68
4. Step 4: Simplify right side
   2,105.60x = 3,549,860.01
5. Step 5: Solve for x
   x = 3,549,860.01/2,105.60
6. Step 6: Final answer
   x = 1,685.91